Dielectric, multilayer ceramic capacitor, and electronic component

Abstract

A dielectric according to the present disclosure contains dielectric particles (10). At least one of the dielectric particles (10) contains a main component and a subcomponent. At least one of the dielectric particles (10) is surrounded by a boundary region (11) that contains a specific element constituting the subcomponent. At least one of the dielectric particles (10) surrounded by the boundary region (11) has a plurality of regions with differing content ratios of the subcomponent excluding specific elements, and of the plurality of regions, includes at least two regions having mutually different crystal orientations.

Description

Dielectrics, multilayer ceramic capacitors, and electronic components

[0001] This disclosure relates to dielectrics, multilayer ceramic capacitors using the dielectric, and electronic components using the dielectric.

[0002] Electronic components used in mobile devices and automotive applications, as well as multilayer ceramic capacitors, require high reliability, and the dielectric materials used in them also require similar reliability.

[0003] Japanese Patent Application Publication No. 2017-178684 discloses an invention relating to a dielectric ceramic composition and a multilayer ceramic capacitor including a dielectric layer made of the dielectric ceramic composition, wherein the dielectric ceramic composition includes a phase consisting substantially only of the main component (main component phase) and a phase in which a rare earth element R is solid-dissolved (diffused) in the main component (diffusion phase), and the high-temperature load life is improved by adjusting the area ratio of the main component phase and the diffusion phase and the composition range of the diffusion phase.

[0004] Japanese Patent Application Publication No. 2017-178684

[0005] The inventors investigated a means to effectively improve high-temperature load life using an approach different from that described in Japanese Patent Application Publication No. 2017-178684.

[0006] One of the purposes of this disclosure is to provide a dielectric material with excellent reliability, a multilayer ceramic capacitor using the dielectric material, and electronic components.

[0007] A dielectric according to one embodiment of the present disclosure comprises dielectric particles, at least one of the dielectric particles comprises a main component and a minor component, at least one of the dielectric particles is surrounded by a boundary region containing a specific element constituting the minor component, at least one of the dielectric particles surrounded by the boundary region has a plurality of regions with different content ratios of the minor component excluding the specific element, and of the plurality of regions, at least two of the regions have different crystal orientations.

[0008] A multilayer ceramic capacitor according to one embodiment of the present disclosure includes a dielectric layer containing the dielectric described above and an electrode. An electronic component according to one embodiment of the present disclosure contains the dielectric described above.

[0009] The dielectric material, the multilayer ceramic capacitor using the same, and the electronic components can extend the high-temperature load life and achieve high reliability.

[0010] This is a partial cross-sectional perspective view of a multilayer ceramic capacitor according to an embodiment of the present disclosure. This is a partially enlarged cross-sectional view of a dielectric according to an embodiment of the present disclosure, showing an enlarged view of a portion of the dielectric layer 2 and internal electrode layer 3 in Figure 1. This is a partially enlarged cross-sectional view of a dielectric particle according to an embodiment of the present disclosure, showing an enlarged view of area E in Figure 2. This is a partially enlarged cross-sectional view of a dielectric particle according to an embodiment of the present disclosure. This is a partially enlarged cross-sectional view of a dielectric particle according to an embodiment of the present disclosure.

[0011] The embodiments of this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments described below, and can be implemented in various ways within the scope of its essence.

[0012] [Multilayer ceramic capacitor 1] Figure 1 is a partial cross-sectional perspective view of a multilayer ceramic capacitor 1 according to an embodiment of the present disclosure.

[0013] As shown in Figure 1, the multilayer ceramic capacitor 1 has a capacitor element body 4 in which dielectric layers 2, which function as dielectrics, and internal electrode layers 3 are alternately stacked. The internal electrode layers 3 are stacked so as to be alternately exposed from both sides of the capacitor element body 4.

[0014] As shown in Figure 1, a pair of external electrodes 5 are formed on both end faces of the capacitor element body 4. Each external electrode 5 is electrically connected to each internal electrode layer 3 that is alternately exposed from both sides of the capacitor element body 4, thereby forming a capacitor circuit. The capacitor element body 4 shown in Figure 1 is substantially rectangular parallelepiped, but the shape of the capacitor element body 4 is not particularly limited.

[0015] The material of the internal electrode layer 3 is not limited, but it is a conductive material, and is mainly composed of base metals such as Ni, Cu, and Sn, or noble metals such as Pd and Ag. The internal electrode layer 3 is constructed as a sintered body of a conductive paste containing a conductive material. The number of layers in the internal electrode layer 3 depends on the number of layers in the dielectric layer 2.

[0016] [Dielectric Layer 2] The number of dielectric layers 2, which are stacked alternately with the internal electrode layers 3, and the thickness of each layer are not particularly limited, but for example, the number of layers may be 1 or more, 5 or more, 20 or more, 50 or more, or 100 or more. The thickness of each layer may be 100 nm or more and several tens of μm or less. Figure 2 is a partially enlarged cross-sectional view of the dielectric layer 2 according to an embodiment of the present disclosure, which is an enlarged view of a part of Figure 1.

[0017] As shown in Figure 2, the dielectric layer 2 contains a plurality of dielectric particles 10. Note that in Figure 2, the size of the dielectric particles 10 is shown as larger relative to the thickness of the dielectric layer 2 in order to emphasize them, and does not represent the actual ratio.

[0018] [Dielectric Particles 10] Figure 3 is an enlarged cross-sectional view of dielectric particles 10 extracted from location E shown in Figure 2.

[0019] The dielectric particles 10 contain a main component and a minor component. The dielectric particles 10 have a boundary region 11 surrounding their outer periphery, and the boundary region 11 contains specific elements that constitute the minor component. The "boundary region 11" may also be referred to as a boundary layer or boundary phase. The main component of the dielectric particles 10 refers to the component that accounts for 70 mol% or more of the dielectric particles, and the minor component of the dielectric particles 10 refers to the components of the dielectric particles other than the main component. Alternatively, the main component refers to the component that constitutes the core 12.

[0020] The boundary region 11 is defined to define the boundary between adjacent dielectric particles 10 and does not specify a thickness. In the embodiments of this disclosure, it is sufficient to define the boundary region 11 by including a specific element that constitutes a minor component. For example, it is not necessary to observe the boundary between the boundary region 11 and the region inside it, and a region containing a specific element in greater quantities than other regions can be arbitrarily defined by elemental analysis or the like and considered as the boundary region 11. Note that "surrounding the outer periphery" does not mean that the boundary region 11 completely and seamlessly surrounds the outer periphery of the dielectric particles 10, even if the results of elemental analysis or the like do not show that the boundary region 11 completely and seamlessly surrounds the outer periphery of the dielectric particles 10, and also includes configurations in which the boundary region 11 is partially provided, such as intermittently surrounding it. For example, the boundary region 11 may also be defined by supplementing the regions that contain a specific element in greater quantities than other regions, including the supplemented region. For example, although not limited to these, the proportion of the boundary region 11 defined by supplementation may be 45% or less, or 30% or less.

[0021] Adjacent dielectric particles 10 may be in contact or spaced apart, and as shown in Figure 2, a segregation phase 20 may be interposed between the dielectric particles 10. The segregation phase 20 is excluded from the dielectric particles 10 in this embodiment.

[0022] When the dielectric particles 10 have a core-shell structure, the boundary region 11 is located on the outermost surface of the shell 13, not at the boundary 14 between the core 12 and the shell 13. A grain boundary exists between adjacent dielectric particles 10. When the dielectric particles 10 have a core-shell structure, a grain boundary is formed between the shells 13 of adjacent dielectric particles 10. This grain boundary can be considered as the boundary region 11.

[0023] Elemental analysis can identify, or at least estimate, the boundary region 11. For example, the boundary region 11 can be obtained by acquiring an elemental mapping image using energy-dispersive X-ray spectroscopy (EDS) or electron energy loss spectroscopy (EELS) and confirming the contrast of the elemental mapping image. Alternatively, in addition to acquiring an elemental mapping image, line analysis can be performed to identify the location where there is a difference in the content ratio of a specific element, thereby obtaining the boundary region 11.

[0024] At least one of the dielectric particles 10 enclosed by the boundary region 11 has multiple regions with different content ratios of minor components excluding the specified element. "Content ratio" refers to the ratio when the main component and minor components together are considered to be 100 mol%. The minor components include the specified element and elements other than the specified element. The content ratio of minor components excluding the specified element may change in steps from the outside to the inside of the boundary region 11, or it may change gradually. Multiple regions with different content ratios of minor components can be arbitrarily defined. For example, in cases where the particles can be divided into multiple regions based on clear differences in content ratios by elemental analysis, or when the content ratios change gradually, the boundaries between the regions can be arbitrarily determined based on predetermined content ratios.

[0025] Furthermore, among these multiple regions with different ratios of minor components, there are at least two regions whose crystal orientations are different from each other.

[0026] We will explain this by taking the case where the dielectric particles 10 have a core-shell structure as an example, in regions where the crystal orientations are different from each other.

[0027] As shown in Figure 3, the dielectric particle 10 is composed of a core 12 located in the center of the particle and a shell 13 that surrounds all or part of the core 12. When the shell 13 covers part of the core 12, the coverage rate may be 50% or more, preferably 70% or more, and more preferably 90% or more, although this is not particularly limited. In the dielectric particle 10 shown in Figure 3, the entire outer circumference of the core 12 is covered by the shell 13. The core 12 and the shell 13 are in contact. The core 12 is a crystalline portion that is substantially composed of the main component, with no sub-components in solid solution, or with a small amount of sub-components in solid solution. The shell 13 has sub-components in solid solution, and the content ratio of sub-components, excluding specific elements, is higher than that of the core 12. As shown in Figure 3, the dielectric particle 10 is composed of one core 12 and a shell 13 surrounding the core 12, or it may be composed of, for example, multiple cores 12 and a shell 13 that continuously surrounds these cores 12.

[0028] When the dielectric particles 10 have a core-shell structure, the content ratio of sub-components excluding specific elements is different between the core 12 and the shell 13. Therefore, in the core-shell structure, the above-mentioned "plural regions with different content ratios of sub-components excluding the specific source" can be regarded as the core 12 and the shell 13. And the crystal orientation of the core 12 and the crystal orientation of the shell 13 are different from each other.

[0029] The dielectric particles 10 shown in FIG. 4 are configured to have a core 12 and a shell 13 that covers the core 12 in the same manner as in FIG. 3. However, in FIG. 4, the shell 13 is composed of a plurality of layers of a first shell 13a and a second shell 13b. The first shell 13a is formed so as to surround the core 12, and the second shell 13b is formed so as to surround the first shell 佝. The first shell 13a is formed on the inner side in contact with the core 12, and the second shell 13b is formed on the outermost surface side of the shell 13 in contact with the surface of the first shell 13a. The first shell 13a and the second shell 13b are a plurality of regions with different content ratios of sub-components excluding specific elements. In FIG. 4, the plurality of regions with different content ratios of sub-components excluding specific elements are three layers of the core 12, the first shell 13a, and the second shell 13b, and at least one or both of the crystal orientations of the core's 12 and the first shell 13a in contact with each other, and the first shell 13a and the second shell 13b in contact with each other are different from each other. The shell 13 can be three or more layers. When the shell 13 with different content ratios of sub-components is composed of a plurality of layers, it is preferable that the plurality of each shell 13 is formed so as to cover the surface of the core 12. Thereby, the contact area (interface area) of each shell 13 can be increased. Since the film thickness of the shell 13 is quite thin, even if the boundary 15 between the first shell 13a and the second shell 13b cannot be clearly discriminated by elemental analysis, the boundary 15 can be arbitrarily defined based on the elemental analysis result or the like.

[0030] Furthermore, if, for example, the content ratio of a specific element constituting a minor component is too low, and it is not possible to clearly detect all or part of the boundary region 11 of the dielectric particle 10, and the outer contour of the dielectric particle 10 cannot be clearly captured, then, as shown in Figure 5, for example, if there exists a region C (for example, corresponding to a shell) on a line segment L connecting regions A and B (for example, corresponding to a core) that are substantially composed of the main component, and which has a higher content ratio of the minor component than regions A and B, and has a different crystal orientation than regions A and B, then it can be estimated that there is one or more dielectric particles 10 surrounded by boundary regions containing the specific element constituting the minor component, and it can be determined that the dielectric particle 10 has multiple regions with different content ratios of minor components excluding the specific element, and that among the multiple regions, it includes at least two regions with different crystal orientations. Here, the crystal orientations of all regions on line segment L do not need to be different from the crystal orientations of regions A and B; it is sufficient that the crystal orientations of at least some regions on line segment L are different from the crystal orientations of regions A and B.

[0031] Furthermore, because the content ratio of specific elements constituting the minor components is small, and it is difficult to identify the boundary region 11, we attempted to identify the dielectric particles 10 using the method shown in Figure 5. However, if, for example, it is difficult to identify region A, it becomes difficult to identify the dielectric particles 10 using the method shown in Figure 5. Even in this case, for example, if a part of the grain boundary can be observed, that area can be considered as the boundary region 11, and regions B and C with different content ratios of the minor components shown in Figure 5 can be identified. By demonstrating that the crystal orientations of regions B and C are different, the dielectric particles 10 can also be identified.

[0032] [Regarding Subcomponents] Elements constituting the subcomponents will be described. Although not limited, the subcomponents include Si and elements other than Si. Si is expressed in the boundary region 11 as a specific element. Therefore, by detecting Si, the boundary region 11 surrounding the dielectric particles 10 can be defined. Detection of elements other than Si in the boundary region 11 is not excluded. The "specific element" means an element that is detected more in the boundary region 11 compared to the inside of the dielectric particles 10, or an element that can be a detection target for specifying the boundary region 11. Therefore, by making Si a detection target, the boundary region 11 can be easily specified. Si may be detected as an oxide. The presence of Si in the boundary region 11 can be presumed to have been sintered well, and thus, the insulation resistance can be increased, and excellent insulation properties can be obtained.

[0033] The subcomponents also include elements other than Si, and at least two regions with different crystal orientations have different content ratios of the subcomponents containing elements other than Si. That is, Si can be used to define the boundary region 11 of the dielectric particles 10, and elements other than Si can be used to define regions with different content ratios of the subcomponents.

[0034] The elements other than Si in the subcomponents are not limited, but for example, include at least one or more elements selected from Mg, Al, V, Cr, Mn, Nb, Mo, Sn, Hf, Ta, W, and rare earth elements. As an example, there are a plurality of regions having different concentrations of rare earth elements as elements other than Si.

[0035] At least two regions with different content ratios of minor components (excluding specific elements) and different crystal orientations are in contact. "In contact" means contact across a surface, not just a point. By stacking at least two regions with different crystal orientations, the contact area can be increased. For example, in the core 12 and shell 13 described in Figure 3, and in the inner first shell 13a and outer second shell 13b described in Figure 4, at least two regions with different crystal orientations are stacked, allowing for contact over a wide area. Even if it is not possible or difficult to observe whether or not contact is occurring, if regions with different content ratios of minor components exist and the effects of the embodiments of this disclosure are achieved, those regions can be considered to be in contact.

[0036] In the embodiments of this disclosure, although not limited thereto, at least one of the dielectric particles 10 has a core-shell structure. However, depending on the observed cross-section, even if a dielectric particle 10 has a core-shell structure, there may be dielectric particles 10 in which only the shell 13 is visible, or the boundary region 11 between contacting dielectric particles 10 cannot be clearly defined by elemental analysis. In other words, not all dielectric particles that have all of the following characteristics appear in the observed cross-section: they are surrounded by a boundary region containing specific elements that constitute minor components, they have multiple regions with different minor component content ratios, and they include at least two regions with different crystal orientations. Furthermore, there are dielectric particles 10 that do not have a core-shell structure at all, and dielectric particles 10 whose minor component content ratios and crystal orientations cannot be properly analyzed. Therefore, it is stipulated that it is sufficient for at least one dielectric particle 10 to be observed. Even if it is not possible to clearly observe that the dielectric particle 10 is surrounded by the boundary region 11, for example, the observation method described in Figure 5 can be used to determine that the dielectric particle 10 has multiple regions with different proportions of minor components, and that among these multiple regions, it includes at least two regions with different crystal orientations.

[0037] The crystal structure of the dielectric particles 10 of the present disclosure includes, for example, a region having a perovskite structure. In an embodiment of the present disclosure, a ceramic material having a perovskite structure can be included as a main component. As the ceramic material having a perovskite structure, in addition to BaTiO ３ (barium titanate), (Ba,Ca)TiO ３ , (Ba,Ca)(Ti,Zr)O ３ , (Sr,Ca)(Ti,Zr)O ３ , (Ba,Sr,Ca)(Ti,Zr)O ３ , BaZrO ３ , CaZrO ３ can be exemplified.

[0038] In one embodiment of the present disclosure, the main component of the dielectric particles 10 is represented by the general formula A ｍ BO ３ . Here, A is one element selected from Ca, Sr, Ba or a combination thereof, B is one element selected from Ti, Zr or a combination thereof, and m is 0.9 or more and 1.4 or less. For example, when the dielectric particles 10 have a perovskite structure, the ratio of A to B may deviate from the stoichiometric composition. Note that even when the main component of the dielectric particles 10 is represented by the general formula A ｍ BO ３ , it is not necessarily required that the main component of the dielectric particles 10 has a perovskite structure. For example, it may have an ilmenite structure, and further, the ratio of A to B may deviate from the stoichiometric composition. As described above, higher reliability can be obtained by specifically limiting the sub-component, or the main component, or the sub-component and the main component. Although it is desirable that the dielectric particles 10 consist only of the main component and the sub-component, they may contain a trace amount of components other than the main component and the sub-component, that is, impurities. The content ratio of the impurities is not particularly limited, but is smaller than each of the main component and the sub-component. For example, it may be 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less with respect to the entire dielectric particles.

[0039] While not limited to these, the boundary between at least two regions with different crystal orientations includes a curve. Here, the lines appearing in the cross-sectional views shown in Figures 3 to 5 represent the appearance of a plane as a line when a three-dimensional dielectric particle 10 is cut. A "curve" is a line that is not a straight line, and includes curved lines and lines that are straight but bent midway. In the core-shell structure shown in Figures 3 to 5, the boundary 14 between the core 12 and the shell 13, and the boundary 15 between the first shell 13a and the second shell 13b appear as curves.

[0040] Thus, if the boundary between at least two regions with different crystal orientations includes a curve, the two regions can be considered not to be twinned. Generally, twinning interfaces are straight lines. Therefore, the boundary between at least two regions with different crystal orientations in the embodiments of this disclosure is not a twinning interface.

[0041] Observation using a high-resolution transmission electron microscope (HR-TEM), or crystal orientation analysis by electron diffraction using a transmission electron microscope (TEM), allows observation of at least two regions with different crystal orientations. While there are several methods classified as electron diffraction, any method that can appropriately analyze the crystal orientation of the target region may be selected. For example, nanobeam electron diffraction (NBED) or limited-field electron diffraction (SAED) may be used. Alternatively, an orientation map may be obtained using electron backscatter diffraction (EBSD). Furthermore, depending on the size of the dielectric particles 10, a scanning electron microscope (SEM) may be used instead of a TEM, and methods such as EBSD can be employed.

[0042] For example, the dielectric layer 2 can be cut at an arbitrary position, the cut cross-section can be observed with a scanning transmission electron microscope (STEM), and elemental mapping can be obtained using EDS. This allows us to obtain the boundary region 11 of the dielectric particles 10, and if the dielectric particles 10 have a core-shell structure, we can distinguish between the core 12 and the shell 13.

[0043] Furthermore, observation using HR-TEM or crystal orientation analysis by electron diffraction can reveal, for example, that the crystal orientation of the core 12 and the crystal orientation of the shell 13 are different. For example, using an orientation map obtained by the EBSD method, it can be observed that the crystal orientations of the core 12 and the shell 13 are different, as shown in the schematic diagram in Figure 3.

[0044] The region containing the dielectric particles 10 with a specific crystal structure can be confirmed during the crystal orientation analysis described above. While known methods can be used to identify the crystal structure, for example, the electron diffraction pattern of the crystal structure assumed from the principal components can be simulated beforehand and compared with the electron diffraction pattern actually obtained by NBED or SAED to identify the crystal structure of the relevant region. Alternatively, instead of obtaining an electron diffraction pattern, a pseudo-electron diffraction pattern can be obtained by performing a fast Fourier transform on part or all of the lattice image obtained by HR-TEM observation.

[0045] [Regarding the effects] According to the embodiments of this disclosure, at least one of the dielectric particles 10 contained in the dielectric layer 2 is surrounded by a boundary region 11 containing a specific element that constitutes a minor component, and has a plurality of regions with different content ratios of minor components excluding the specific element, and of the plurality of regions, at least two regions have different crystal orientations. As a result, oxygen vacancies can be trapped by disrupting the atomic arrangement at the boundary of regions with different crystal orientations, the high-temperature load life can be extended, and high reliability can be obtained. The difference in crystal orientation between the at least two regions with different crystal orientations is not particularly limited, but may be 5° or more, 10° or more, or 15° or more.

[0046] In the embodiments of this disclosure, at least two regions with different crystal orientations are in contact, which allows for more effective trapping of oxygen vacancies and higher reliability. For example, as shown in Figure 3, the dielectric particle 10 has a core 12 consisting of a continuous region with a constant crystal orientation and a shell 13 consisting of a continuous region with a constant crystal orientation, where the core 12 and shell 13 have different crystal orientations. The core 12 and shell 13 are in contact on a surface. Alternatively, as shown in Figure 4, the shell 13 has a first shell 13a consisting of a continuous region with a constant crystal orientation and a second shell 13b consisting of a continuous region with a constant crystal orientation, where the crystal orientations of the first shell 13a and the second shell 13b are different. The first shell 13a is formed on the inside, close to the core 12, and the second shell 13b is on the outside of the shell 13 and is in contact with the first shell 13a on a surface.

[0047] It is possible that no dielectric particles 10 satisfying the configuration of this disclosure can be found in the observed cross-section. In such cases, it is necessary to consider whether observation is possible in another cross-section. It is desirable that multiple dielectric particles 10 satisfying the configuration of this disclosure are confirmed in the observed cross-section, but one is sufficient. However, it is desirable that at least one dielectric particle 10 satisfying the configuration of this disclosure is observed in each of the multiple cross-sections. As mentioned above, methods such as HRTEM and electron diffraction are used to determine the crystal orientation, but these methods can only determine the crystal orientation of particles whose low-index plane is facing the observation direction. Therefore, if even one dielectric particle 10 satisfying the configuration of this disclosure is confirmed, it can be inferred that a certain amount of dielectric particles 10 satisfying the configuration of this disclosure are also included among the particles whose crystal orientation could not be determined. Furthermore, when a voltage is applied to electronic components and multilayer ceramic capacitors at high temperatures, oxygen vacancies contained in the dielectric move from the positive electrode side to the negative electrode side and accumulate, reducing the insulating properties and leading to failure. Therefore, if the movement of oxygen vacancies can be inhibited at some point along their migration path, the high-temperature load life can be improved. Thus, even if only a portion of the dielectric particles 10 satisfy the configuration of this disclosure, the effect of improving the high-temperature load life can be achieved.

[0048] In the embodiments of this disclosure, the boundary between at least two regions with different crystal orientations is not a twinning interface. For example, the boundary 14 between the core 12 and the shell 13 shown in Figure 3 is a curved surface and is not a twinning interface. Alternatively, the boundary 15 between the first shell 13a and the second shell 13b shown in Figure 4 is a curved surface and is not a twinning interface. Because the boundary between at least two regions with different crystal orientations is not a twinning interface with less disorder in the atomic arrangement, oxygen vacancies can be strongly trapped, and high reliability can be obtained.

[0049] In the embodiments of this disclosure, the dielectric particles 10 include, but are not limited to, minor components, which include Si and at least one element from among Mg, Al, V, Cr, Mn, Nb, Mo, Sn, Hf, Ta, W, and rare earth elements. The boundary region 11 surrounds the dielectric particles 10 with Si as the specified element, and at least two regions with different crystal orientations have different content ratios of minor components, which include at least one element other than Si from among Mg, Al, V, Cr, Mn, Nb, Mo, Sn, Hf, Ta, W, and rare earth elements. Thus, the boundary region 11 can be identified, or at least estimated, by detecting Si in elemental analysis. By detecting Si, excellent sinterability and high insulation resistance can be obtained. Furthermore, by using the concentration of an element other than Si used to define the boundary region 11 as a reference, multiple regions with different content ratios of minor components can be appropriately and easily selected. In embodiments of this disclosure, at least two regions having different crystal orientations may have lattice defects such as planar defects between them.

[0050] [Manufacturing Method for Multilayer Ceramic Capacitors] Below, a representative example of the manufacturing method for the multilayer ceramic capacitor 1 shown in Figure 1 will be described. The multilayer ceramic capacitor 1 of this embodiment can be manufactured by creating green chips using a paste printing method or sheet method, firing these chips, and then forming a pair of external electrodes 5 on the resulting element body 4.

[0051] First, the main component raw materials and the secondary component raw materials are prepared as dielectric materials. These raw materials can be oxides or mixtures thereof of the above-mentioned components, or composite oxides. Alternatively, various compounds that become oxides or composite oxides of the above-mentioned components upon firing, such as carbonates, oxalates, nitrates, hydroxides, organometallic compounds, etc., can be appropriately selected and mixed for use.

[0052] Next, the main component raw materials are wet-mixed using a ball mill or the like, and the resulting mixed powder is dried and then calcined under predetermined conditions to obtain the main component powder. The mixing of the raw materials is not particularly limited, but they are thoroughly mixed by a wet method for about 20 hours and then dried. The calcination conditions are not particularly limited, but the calcination temperature is 900°C to 1350°C, preferably 1000°C to 1350°C, the holding time is preferably 1 to 10 hours, the heating rate to the calcination temperature is about 10°C / hour to 2000°C / hour, and the cooling rate after the holding time is 200°C / hour or more, preferably 300°C / hour or more, more preferably 400°C / hour or more. The main component powder after calcination may be pulverized using a ball mill or the like as needed. Alternatively, instead of obtaining the main component powder from the main component raw materials by the above process, a predetermined commercially available product may be used as the main component powder.

[0053] Next, the main component powder, the secondary component raw materials, and additional main component raw materials as needed are wet-mixed using a mixer such as a ball mill to obtain dielectric raw materials. Furthermore, the dielectric raw materials are made into a paint to prepare a paste for the dielectric layer. The dielectric layer paste may be an organic paint made by kneading the dielectric raw materials with an organic vehicle, or it may be a water-based paint.

[0054] An organic vehicle is a binder dissolved in an organic solvent. The binder used in the organic vehicle is not particularly limited and can be appropriately selected from various common binders such as ethylcellulose and polyvinyl butyral. The organic solvent used is also not particularly limited and can be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene, depending on the method of use, such as printing or sheet processing.

[0055] The paste for the internal electrode layer is prepared by kneading a conductive material made of the various conductive metals and alloys described above, or various oxides, organometallic compounds, resinates, etc. that become the conductive material after firing, with the organic vehicle described above. The paste for the internal electrode layer may also contain a co-material. The co-material is not particularly limited, but it is preferable that it has a composition similar to that of the main component.

[0056] Next, using the pastes described above, green chips that will become the element body 4 after firing are manufactured. The green chips can be manufactured by various printing methods or various sheet methods.

[0057] For example, when manufacturing green chips using the sheet method, first, a dielectric paste is applied to a carrier film such as PET to form a sheet, which is then dried as needed to obtain a green sheet. Then, a paste for internal electrodes is applied to the green sheet in a predetermined pattern using various printing methods such as screen printing. After laminating multiple layers, a mother laminate is obtained by pressing in the lamination direction. At this time, the green sheets are laminated so that only dielectric layers are located on the top and bottom surfaces of the mother laminate in the lamination direction. Finally, the mother laminate obtained in the above process is cut by dicing or press cutting to obtain multiple green chips.

[0058] Next, the green chips are subjected to a binder removal treatment. The conditions for the binder removal treatment are preferably a heating rate of 5°C / hour to 300°C / hour, a holding temperature of preferably 180°C to 900°C, and a temperature holding time of preferably 0.5 hours to 48 hours. The atmosphere for the binder removal treatment is either an air atmosphere or a reducing atmosphere.

[0059] After binder removal, the green chips are fired. The atmosphere during green chip firing should be appropriately determined according to the type of conductive material in the paste for the internal electrode layer, but when a base metal such as Ni or Ni alloy is used as the conductive material, the oxygen partial pressure in the firing atmosphere should be 10 －１４ MPa ~ 10 －１０It is preferable to use MPa. If the oxygen partial pressure is below the above range, the conductive material of the internal electrode layer may undergo abnormal sintering and break. Also, if the oxygen partial pressure exceeds the above range, the internal electrode layer tends to oxidize.

[0060] Furthermore, the holding temperature during firing is preferably 1000°C to 1400°C, more preferably 1100°C to 1360°C. If the holding temperature is below the above range, densification will be insufficient, and if it exceeds the range, abnormal sintering of the internal electrode layer may cause breaks in the electrodes, deterioration of the capacitance temperature characteristics due to diffusion of the internal electrode layer constituent material, and reduction of the dielectric ceramic composition.

[0061] Other firing conditions include a heating rate of preferably 50°C / hour to 2000°C / hour, more preferably 200°C / hour to 300°C / hour, a temperature holding time of preferably 0.5 hours to 8 hours, more preferably 1 hour to 3 hours, and a cooling rate of preferably 50°C / hour to 2000°C / hour, more preferably 200°C / hour to 300°C / hour. Furthermore, the firing atmosphere is preferably a reducing atmosphere, and the atmosphere gas is, for example, N ２ and H ２ A mixed gas can be used after humidification.

[0062] After firing in a reducing atmosphere, it is preferable to anneal the capacitor element body. Annealing is a process to re-oxidize the dielectric layer, which significantly extends the lifespan and improves reliability.

[0063] The partial pressure of oxygen in the annealing atmosphere is 10 －９ MPa ~ 10 －５ It is preferable to set the oxygen partial pressure to MPa. If the oxygen partial pressure is below the above range, re-oxidation of the dielectric layer is difficult, and if it exceeds the above range, oxidation of the internal electrode layer tends to progress.

[0064] The holding temperature during annealing is preferably 1100°C or lower, and particularly preferably between 500°C and 1100°C. If the holding temperature is below this range, the oxidation of the dielectric layer will be insufficient, resulting in low insulation resistance and a shortened high-temperature load life. On the other hand, if the holding temperature exceeds this range, not only will the internal electrode layer oxidize and the capacitance decrease, but the internal electrode layer will also react with the dielectric substrate, leading to deterioration of capacitance-temperature characteristics, a decrease in insulation resistance, and a shortened high-temperature load life. Note that annealing may consist only of a heating process and a cooling process. That is, the temperature holding time may be zero. In this case, the holding temperature is synonymous with the maximum temperature.

[0065] Other annealing conditions include a temperature holding time of preferably 0 to 20 hours, more preferably 2 to 10 hours, and a cooling rate of preferably 50°C / hour to 500°C / hour, more preferably 100°C / hour to 300°C / hour. The atmospheric gas for annealing is, for example, N ２ Or N ２ +H ２ It is preferable to use O gas or the like.

[0066] Furthermore, the debinding process, firing, and annealing may be performed consecutively or independently.

[0067] The element body 4 is obtained by firing and annealing through the process described above. The element body 4 obtained as described above is then subjected to end face polishing, for example by barrel polishing or sandblasting, and an external electrode paste is applied and fired to form the external electrode 5. Then, if necessary, a coating layer is formed on the surface of the external electrode 5 by plating or the like.

[0068] The multilayer ceramic capacitors of this embodiment, manufactured in this manner, are mounted on printed circuit boards or the like by soldering and used in various electronic devices.

[0069] In the embodiments of this disclosure, the main component powder is pre-treated before mixing the main component powder with the auxiliary component raw materials. The pre-treatment is performed to form at least two regions with different content ratios of the auxiliary components so that their crystal orientations are different from each other, and the method of pre-treatment is not limited as long as the crystal orientations can be made different.

[0070] In the embodiments of this disclosure, pulsed laser irradiation can be used as an example of pretreatment. That is, a pulsed laser is irradiated onto the main component powder. This allows the surface of the main component powder to be instantaneously dissolved and solidified. At this time, it is assumed that the surface of the main component powder is amorphous. When the main component powder that has undergone such pretreatment is mixed with the auxiliary component raw material and fired, a region with a high content of the auxiliary component is formed on the surface of the main component powder. Because the surface of the main component powder has an amorphous structure, the region with a high content of the auxiliary component can be formed so that it has a different crystal orientation from the interior of the main component powder.

[0071] Any method other than pulsed laser irradiation is acceptable, as long as it applies energy to the surface of the main component powder, for example, by causing a phase change or altering the surface state.

[0072] In the embodiments of this disclosure, the dielectric can be applied to the multilayer ceramic capacitor 1 shown in Figure 1, but is not limited to this and may be applied to other electronic components. For example, the electronic components according to this disclosure may be filters, diplexers, resonators, oscillators, antennas, etc., in addition to capacitors.

[0073] The contents of this disclosure will be described in more detail below with reference to the examples and comparative examples. However, this disclosure is not limited to the examples described below.

[0074] <Manufacturing conditions common to the examples and comparative examples> As the main component raw material of the main component powder, barium carbonate (BaCO3) ３ ), calcium carbonate (CaCO3) ３ ), strontium carbonate (SrCO ３ ), titanium oxide (TiO ２ ) and zirconium oxide (ZrO ２ The following were prepared: Oxides of Si, Mg, Al, V, Mn, Nb, Mo, Y, Gd, Tb, Dy, Ho, and Yb were prepared as auxiliary raw materials.

[0075] The main component raw materials were weighed so that the composition of the main components after calcination would be as shown in Table 1. After weighing, each raw material was mixed. Mixing was performed by wet mixing and stirring in a ball mill. The mixture after wet mixing and stirring was dried. After drying, it was calcined in air at 1100°C to 1300°C and wet-milled in a ball mill to obtain the main component powder.

[0076] Next, the main component powder and secondary component raw materials were weighed so that the composition after firing would be as shown in Table 1. Here, the metal ion concentration of each secondary component was set to 0.1 mol% to 1.0 mol% relative to the main component. The weighed main component powder and secondary component raw materials were mixed with an organic vehicle to form a paste, which was used to obtain a dielectric layer paste. Using the dielectric layer paste, a green sheet was formed on a PET film. Then, using a paste for the internal electrode layer obtained by mixing Ni powder and an organic vehicle, the internal electrode layer was printed on this sheet in a predetermined pattern. After that, the sheet was peeled off the PET film to produce a green sheet with an internal electrode layer. Next, multiple green sheets with internal electrode layers were laminated and pressure-bonded to obtain a green laminate. On the top and bottom surfaces of the green laminate in the lamination direction, a protective green sheet without the printed internal electrode layer was laminated. By cutting this green laminate to a predetermined size, green chips were obtained.

[0077] Next, the obtained green chips were subjected to debinder treatment, firing, and annealing to obtain a sintered body that would become the element body. After polishing the end faces of the obtained sintered bodies with sandblasting, an In-Ga alloy was applied to form the external electrodes. Here, the conditions for the debinder treatment were a heating rate of 30°C / hour, a holding temperature of 260°C, a holding time of 8 hours, and an atmosphere of air. The conditions for firing were a holding temperature of 1200°C to 1300°C, a holding time of 2 hours, a cooling rate of 300°C / hour or more, and a humidified N atmosphere gas. ２ +H ２ Mixed gas, oxygen partial pressure 1.0 × 10 －１３ MPa ~ 1.0 × 10 －１２ The pressure was set to MPa. The annealing conditions were: holding temperature of 1050°C, holding time of 2 hours, and atmospheric gas humidified N2. ２ Gas, oxygen partial pressure 1.0 × 10－９ The pressure was set to MPa or higher. The average dimensions of the obtained device body were 2.0 mm × 1.2 mm × 0.6 mm, the number of dielectric layers sandwiched between the internal electrode layers was 5, the average thickness of the dielectric layers was 5 μm, and the average thickness of the internal electrode layers was 1.5 μm.

[0078] <Measurement of High-Temperature Load Life> The high-temperature load life was evaluated by measuring the insulation degradation time of the capacitor sample obtained above while maintaining the application of a DC voltage under an electric field of 50 V / μm at 200°C. In this embodiment, the failure time was defined as the time from the start of voltage application until the insulation resistance dropped by one order of magnitude.

[0079] In this experiment, the above evaluation was performed on 20 capacitor samples, and the Mean Time To Failure (MIT) was calculated by performing a Weibull analysis on these samples.

[0080] The cross-section of the dielectric layer 2 along the stacking direction of the capacitor sample was polished, and a thin section sample with a thickness of approximately 50 nm was prepared using a focused ion beam (FIB). A scanning transmission electron microscope (STEM) was used to observe a region of 1 μm to 5 μm square at an acceleration voltage of 200 kV. An elemental map of Si and other minor components was then obtained using the attached EDS device, confirming the existence of dielectric particles 10 surrounded by boundary regions containing Si and having multiple regions with different content ratios of minor components other than Si. The crystal structure and crystal orientation were then identified and evaluated for each of the multiple regions with different content ratios of minor components using electron diffraction.

[0081] <Differences in manufacturing conditions between the examples and comparative examples> In the examples, pulsed laser irradiation was performed as a pretreatment of the main component powder, but in the comparative examples, pulsed laser irradiation was not performed.

[0082] Although not limited to pulsed lasers, this experiment used an Nd:YAG laser with a wavelength of 1064 nm. The laser output was set to 1 W and the pulse frequency to 1000 Hz. Table 1 below shows the evaluation results of the mean failure time for Examples 1 to 14 and Comparative Examples 1 to 14.

[0083]

[0084] In Table 1, examples and comparative examples with matching sample numbers correspond to each other (i.e., for example, Example 1 corresponds to Comparative Example 1, Example 2 corresponds to Comparative Example 2, etc.), and the mean failure time for each example was obtained with the mean failure time of the corresponding comparative example set to 100.

[0085] Table 1, which shows the "presence or absence of regions with different crystal orientations," indicates the results of observing whether at least one dielectric particle observed in each sample had a different crystal orientation in a region with a different content ratio of subcomponents other than Si, as determined by electron diffraction. The "presence or absence of regions with different crystal orientations" tended to correlate with the mean time of failure. In other words, it was found that there was a clear difference in mean time of failure between the examples and the comparative examples. This suggests that in the examples, the surface of the main component powder becomes amorphous during the manufacturing process, and regions with a high content ratio of subcomponents are formed, having a different crystal orientation from the interior of the main component powder. Furthermore, all regions with different crystal orientations observed in the examples had a perovskite-type structure. In addition, it was observed that the boundaries of the regions with different crystal orientations observed in the examples were curved, not twinning interfaces.

[0086] This application claims priority to Japanese Patent Application No. 2025-007064, filed on 17 January 2025, which is incorporated herein by reference in its entirety.

Claims

Contains dielectric particles, At least one of the dielectric particles comprises a main component and a minor component, At least one of the dielectric particles is surrounded by a boundary region containing a specific element that constitutes the subcomponent, A dielectric in which at least one of the dielectric particles surrounded by the boundary region has a plurality of regions with different content ratios of the minor components excluding the specific element, and of the plurality of regions, at least two of the regions have different crystal orientations. 　 The aforementioned minor component includes Si and elements other than Si. The boundary region surrounds at least one of the dielectric particles with Si as the specific element. The dielectric according to claim 1, wherein at least two of the regions having different crystal orientations have different content ratios of the subcomponents containing elements other than Si. 　 The dielectric according to claim 2, wherein the aforementioned minor component comprises Si and at least one element selected from Mg, Al, V, Cr, Mn, Nb, Mo, Sn, Hf, Ta, W, and rare earth elements. 　 The dielectric according to claim 1, wherein at least two of the regions having different crystal orientations are in contact with each other. 　 At least one of the dielectric particles has a core-shell structure having a core and a shell that surrounds and covers the core. The dielectric according to claim 1, wherein at least the crystal orientation of the core and the crystal orientation of the shell are different from each other. 　 The dielectric according to claim 1, wherein at least one of the dielectric particles includes a region having a perovskite-type structure. 　 At least one main component of the dielectric particle is general formula A ｍ BO ３ It is represented as, A is one element selected from Ca, Sr, and Ba, or a combination thereof. B is one element selected from Ti and Zr, or a combination thereof. The dielectric according to claim 1, wherein m is 0.9 or more and 1.4 or less. 　 A dielectric layer comprising the dielectric described in claim 1, Electrodes and, including, Multilayer ceramic capacitor. 　 A dielectric material comprising the dielectric material described in claim 1, Electronic components.

Images